Some turbochargers are provided with exhaust-bypass valves to prevent excessive gas from flowing into the turbines. An exhaust-bypass valve is a valve that opens/closes a passage communicating between the turbine inlet and the turbine outlet.
Many exhaust-bypass valves are simply structured swing valves. FIG. 30 shows a conventional exhaust-bypass valve 201 of a turbocharger. A bulkhead 202 divides a passage 203 at the turbine-inlet side from a passage 204 at the turbine-outlet side, and a shunting passage 205 communicates between the passages 203 and 204. The exhaust-bypass valve 201 is provided with a valve flap 206 for covering the shunting passage 205. The valve flap 206 is supported by an arm 206a at one side thereof, and the arm 206a is supported rotatably about a shaft 207. One end of a lever 208 is secured to the shaft 207, and opening/closing is performed as a result of the other end of the lever 208 being driven by an actuator 209. More specifically, when a shaft 209a of the actuator 209 extends, the lever 208 moves in the direction away from the passage 203 at the turbine-inlet side with the shaft 207 serving as a center of rotation, and the valve flap 206 secured to the shaft 207 also moves in the direction away from the passage 203 at the turbine-inlet side accordingly, thus causing the shunting passage 205 to open, as shown in FIG. 31. When the shaft 209a of the actuator 209 retracts, the lever 208 moves towards the passage 203 at the turbine-inlet side with the shaft 207 serving as the center of rotation, and the valve flap 206 secured to the shaft 207 also moves towards the passage 203 at the turbine-inlet side accordingly, causing the shunting passage 205 to close, as shown in FIG. 30. In the closed state, a sealing face 206b of the valve flap 206 comes into close contact with the side of the bulkhead 202 to block the shunting passage 205.
Patent Document 1:
Japanese Unexamined Patent Application, Publication No. 2006-274833